The present invention generally relates to the automatic reading of utility meters. More specifically, the present invention is related to a method and apparatus for transmitting utility meter data from an underground meter pit using a removable pit lid and antenna.
A longstanding problem in the utility industry is the economic reading of utility meters without inconvenience to the homeowner. The problem is especially acute in connection with the reading of water meters. In geographic areas that are subject to freezing temperatures, it has in the past been necessary to install meters within the residence to prevent damage to the meter when the temperature drops such that the water within the meter freezes. However, the reading of such meter installations presents a number of problems, such as the inconvenience to the homeowner as well as the inconvenience to the meter reader when the homeowner is not present at the time of the individual meter reading.
In addition, manual meter reading has a significant disadvantage in that it requires a large amount of manpower, leading to significant expense. Further, meter readers may erroneously record the numeral values of the meter register or the homeowner may not be present at the time the meter reading is to take place.
In order to solve the personnel requirements of physical meter reading, a large number of remote meter reading units have been developed. These meter reading units may be, for example, an automatic meter reading (AMR) unit. The meter register comprises a sensor to detect the rotation of movement of the components within the meter to generate an electrical count of the volume of commodity that flows through the meter. The recorded data from the meter is broadcast by a communication device of the AMR unit using an RF signal. In such types of systems, the meter measurement is broadcast from the communication device using an RF signal that can be read from a remote location. In these remote meter reading systems, the antenna of the communication device typically extends slightly above the pit lid such that the radio frequency signals generated by the antenna can be transmitted away from the meter pit. In many situations, the pit lid is formed from a metallic material, such as iron, that significantly inhibits the transmission of radio frequency signals therethrough.
In current AMR applications being developed, a radio transmission circuit including an antenna is used to transmit meter-related information over a relatively long distance, such as up to one-half mile. The use of an AMR radio to transmit metered-related information over a relatively long distance allows the meter data to be read from a remote location and eliminates the requirements of a meter reader physically interrogating the meter from a location approximate to the meter.
As the use of fixed network AMR systems for commercial, residential and remote applications increases, the need for a robust antenna assembly has become increasingly important. Since many meter pit locations were established as the original water infrastructure was constructed, improvements to the roadways and sidewalks, as well as a reduction in costs, has forced the need for safe, low profile and rugged metering products. Currently, AMR antennas are being used on sidewalks where pedestrian traffic may interact with the antenna assembly and in areas of heavy vehicular traffic. Thus, antenna designs must achieve a balance between physical size, RF performance and mechanical strength to make the products ideally suited for long-range communication, supporting vehicle traffic and pedestrian safety.
When such arrangements are in use, material close to the antenna may affect the efficiency of the antenna in radiating the desired signals. The use of pit-mounted antenna arrangements are often complicated by the type of material used to form the pit lid and the operating environment in the area surrounding the antenna. As an example, pit lids can be formed from a variety of materials, such as cast iron, plastic or concrete, which dramatically affects the radiating pattern of pit lid antennas that include radiating elements either positioned below or have a portion of the antenna extending past the top edge of the pit lid.
In addition to the problems associated with the radiation pattern of the pit lid antenna, it is also desirable to provide a pit lid antenna that can be easily mounted to the pit lid and removed as desired. Further, it is desired to provide a pit lid antenna that includes dependable signal contacts to ensure adequate transmission of meter data.